Most metrology systems designed to characterize the geometry of a lens are incomplete and/or destructive (or both). Currently, to find the thickness of a lens, the lens must be cut into one or more thin slices and measured under a microscope. Besides the obvious problem of destroying the lens, this process is extremely labor intensive and only results in capturing one or two “slices” through the lens. Currently, only 5-10 points can be measured per slice because of the time and skill required. Additionally, most types of contact lenses tend to exhibit shrinkage when removed from a hydrated environment, making measurement inaccurate.
Another method to measure lens thickness is to use a contact type touch probe. This method may be very slow and involves correcting for squash factors when the lens is compressed by the probe. Other methods that are capable of mapping the thickness of a lens over an entire surface are slow (approximately 1 sec. per point, with thousands of points per lens), and are also subject to the squash factor correction.
Additionally, current methods of measuring or inspecting the base curve of a lens are very difficult. Current methods include a 3-point circular fit of the base curve to characterize the base curve and fit performance of a lens.
The present invention seeks to correct the inadequacies of the prior art.